1. Field of the Invention
The present invention relates generally to oil, gas and geothermal well drilling rigs and, more specifically, to a mobile well drilling rig and to the transport, assembly, and disassembly of such a rig.
2. Description of the Prior Art
With the ever increasing pressure in recent years on domestic oil and gas production, it has become increasingly important to provide mobile drilling rigs which can be easily transported over the highway and which can be rapidly assembled and disassembled at the well site. For example, present well exploration and completion in the Barnett Shale region in Texas has expanded even into urban areas. In these and other settings, to be economically competitive, oil and gas drilling and exploration activities require the rapid deployment, assembly and disassembly of drilling structures. One way to accomplish these goals is to provide a mobile, highly capable rig which maximizes productive on-site drilling time in urban or rural settings, while minimizing essentially non-productive erection, disassembly and road transportation time. As a result, the transportability of components and the speed at which components can be assembled with the minimum amount of auxiliary equipment becomes a paramount concern.
A transportable drilling rig typically includes, for example, a support base, a derrick, pipe sections, and a drill floor Often times however, auxiliary support equipment such as cranes are required to facilitate the setup and takedown of large components such as the base, the drill floor, the pipe racking board, and the like, having the effect of increasing operational costs. Further, drilling sites are often located in remote areas requiring truck transportation of the components of the rig accompanied by equipment used to assemble the rig. In some cases, the process is further complicated by the need to change locations once a hole is drilled and it is determined whether the site will be sufficiently productive to merit a pumping installation, whether the site will be unproductive all together, or whether a more ideal location exists to drill a hole. Typically, site changes can occur once every several months, and, in response, prior art systems have attempted to increase the degree of mobility of rig components. Auxiliary equipment however is still necessary for performing many of the steps involved in assembly and disassembly of the rig.
Since the variable costs associated with leased support equipment, such as cranes and the like, are calculated on a per hour or per day basis, expediting the takedown, transport, and setup operations is crucial for minimizing equipment leasing costs. Typical takedown and setup time is on the order of days. With equipment leasing costs ranging from several hundred dollars per day or more, many thousands of dollars in costs may be incurred for each end of a setup and takedown operation. For larger or more complex rigs, the cost may be even higher. Even where the prior art drilling rigs are geared towards facilitating rapid setup, takedown and transport, they have still generally required external cranes, external winches, and the like which increase the overall expense.
A number of factors contributed to the takedown and setup time required by the prior art systems. For example, in the past, disassembly of the drilling rig mast assemblies normally required unstringing and removal of the traveling block cables and traveling block prior to lowering the mast from the drill rig or at least prior to disassembly or telescoping of the mast preparatory to moving on to a new well site. Also, erection of the mast assemblies of the prior art mobile drilling rigs tended to delay start-up of drilling operations since the drill-pipe cannot be moved into a suitable ground position for racking until such time as the mast is raised to the vertical and the pipe racking ground area is cleared. Further, the access road to a drilling rig normally courses directly up to the drawworks side of the rig. Where the intended well site is located on marshy ground, it is normally necessary to expend substantial time and effort in grading and stabilizing a substantial ground area completely around the rig in order to provide access and working area for the necessarily heavy equipment required to move and erect the mast. These are merely intended to be exemplary problems of the type encountered by the prior art, as there were numerous other problems associated with assembly and disassembly of drilling rigs of the type under consideration.
Although a number of prior art references exist which show purported “portable” or mobile drilling rigs, such devices tended to suffer from one or more deficiencies. One such prior art system for erecting an oil well derrick is shown in U.S. Pat. No. 3,922,825, to Eddy's et al, issued on Dec. 2, 1975. Eddy's system employs a stationary substructure base with a companion movable substructure base mounted thereon. Eddy's movable substructure base is coupled to the stationary base but swings upright into an elevated position on a series of struts that are connected to the stationary base. Eddy's movable base is otherwise stationary, since neither the stationary base nor the “movable” base are mobile or repositionable without the use of an auxiliary crane. Also, simply raising the movable substructure base and the drill mast requires the use of a winch mounted on an auxiliary winch truck.
Another prior art system for assembly of a drill rig is shown in U.S. Pat. No. 3,942,593, to Reeve, Jr., et al, issued on Mar. 9, 1976. The Reeve apparatus includes a trailerable telescoping mast and a separate sectionable substructure assembly further comprising a rig base, a working floor, and a rail means. The mast is conveyed to the top of the substructure by rollers and may be raised by hydraulic raising means to the upright position. A disadvantage of the Reeve system is the need for drawlines and a winch to raise the mast onto the working floor.
U.S. Pat. No. 4,269,395, to Newman et al., issued May 26, 1981, shows a portable rig which includes a telescoping mast for telescoping to a reduced length for transport. The mast is also cantilevered in use so that the traveling block moves vertically at one side of the mast.
U.S. Pat. No. 4,290,495, to Elliston, issued Sep. 22, 1981, shows a portable workover rig with a base platform and a collapsible mast which is movable from a reclining position during transport to an erect position in operation.
U.S. Pat. No. 4,821,816, to Willis, issued Apr. 18, 1989, shows an “Apache” modular drilling machine. The machine has a substructure skid and a platform which supports a draw works. A pipe boom is mounted on another skid and is designed to fit between skid runners on the drilling substructure skid. The drilling substructure skid supports four legs which are pivotally mounted at the platform and at the substructure. A pair of platform cylinders are provided to raise and lower the drilling platform.
U.S. Pat. No. 4,899,832, to Biersheid, issued Feb. 13, 1990, shows a modular drilling apparatus that is transported in modular units to the well site. The apparatus includes a drilling unit and two raising units that are locked to the respective opposite sides of the drilling unit. After base structures on the raising units are lowered to the ground to provide a support, the towers of the raising units and the mast of the drilling unit are simultaneously elevated to the vertical.
U.S. Pat. No. 6,634,436, to Desai, issued Oct. 21, 2003, shows a mobile land drilling rig with a mobile telescoping substructure box which assists in the rapid placement, assembly, disassembly and repositioning of the drilling rig and associated drilling equipment.
U.S. Pat. No. 6,860,337, to Orr et al., issued Mar. 1, 2005, describes a process for lowering or raising a drilling rig for transportation. The top drive is moved within the mast with a vertical guide and torque reaction mechanism to a locked position prior to transport.
As has been mentioned, a number of the devices shown in the above described prior art require the need for auxiliary equipment such as cranes, winch trucks and the like to erect the derrick. Several of the systems described above require a large substructure that must be set down with a crane prior to the imposition of any additional structure thereupon. Further movement or repositioning of the base structure requires cranes or other heavy equipment to effect movement of the component parts.
It is therefore an object of the present invention to provide a mobile land rig that is self sufficient and thus capable of being transported, erected, and disassembled without the need for extensive auxiliary equipment such as cranes and winch trucks. Such a system would save costs associated with leasing cranes and the like for periods of days during erection and disassembly of rigs.
Another object of the invention is to provide a drilling rig system with a self contained substructure base capable of being easily moved. Such a system would allow rapid placement and repositioning of the substructure base without the need for a crane or the like.
Another object of the invention is to provide such a drilling system wherein all system components are easily trailerable and transportable by truck. Such a system could be easily moved from one site to another with a minimum of setup and takedown time.
The above needs and objectives are met in the invention as described in the discussion which follows.